On Feb 14, 2020, at 4:56 PM, uncarollo2 <chris1011@...> via Groups.Io <chris1011@...> wrote:



I like the resolution on that Running Man image. Very nice.

Try masking down the outer 1/8 inch of the mirror, see if that reduces the spray of light around the brightest stars. If that works, think about adding a disc in front of the mirror with a diameter perhaps 1/4 inch smaller than the mirror.

I have seen this on all Russian RCs (RC Optical scopes) where a disc of slightly smaller aperture really helped. Most of the RC mirrors from Lomo had turned edge and were only spec'd to 95% of the full aperture. The very outer part produced a heavy spray of light around bright stars.

Rolando

-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Fri, Feb 14, 2020 3:47 pm
Subject: Re: [ap-gto] Close up of M81 without CCDT67

So, would you say the new advantages of the small pixel CMOS cameras is that they bring high sensitivity to small pixels?

I also got a shot of the Running Man with the 1600mm setup:

https://pbase.com/rchozick/image/170381415

I got M101 at 1600 but the seeing was worse and guiding not as good. 

https://pbase.com/image/170399423

Robert

On Feb 14, 2020, at 3:10 PM, uncarollo2 via Groups.Io <chris1011@...> wrote:

You are running 0.6 arc sec per pixel, which to me is not oversampling for high resolution imaging. In fact, for galaxies i prefer 0.3 to 0.4 arc sec per pixel which really brings out fine detail. My 17"F8 astrograph and the QSI 683 has such pixel scale and really does a superb job on small faint galaxies, even here in Northern Illinois. You have to have good tracking, of course, and on the best nights I can get below 0.15 arc sec RMS with the 1600 encoder mount.

I see a lot of images that are way undersampled (3 to 4 arc sec per pixel) with poor guiding that produces thick stars and very little resolution. To me these images resemble Brownie camera snapshots versus images taken with an 8x10 view camera. (shows my age, doesn't it)  :^))

Rolando

-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Fri, Feb 14, 2020 2:14 pm
Subject: Re: [ap-gto] Close up of M81 without CCDT67

Thanks Roland.  My last dark sky outing was my first use of this scope and camera.   I am really confused on the whole image scale question.  I bought this camera because it has the largest pixels of any of the CMOS cameras. The image scale is .6 with this camera and 1600mm.   My scale is about 1.8 with my FSQ 106 - 530mm.  If the recommended guidance of a scale of 1-2 for image scale is used the 1600mm should be too small an image scale.  Most CMOS cameras have only 2.5-3.5 micron pixels vs 4.63 on my ASI294.  Is oversampling bad?  The .6 scale in my image sure looks ok.    What about .4 or .3?  I intentionally did not get larger than a 1600mm focal length because of this issue (and yes, guiding issues are not as bad vs 2000 and over).  Everyone asks why I got an 8 RC instead of a 10 or 12 inch RC.  The above reason is why.   Each new CMOS camera that comes out still has really small pixels.   How good would 2.5 micron pixels look on a 2500 mm scope?  

Robert

On Feb 14, 2020, at 1:18 PM, uncarollo2 via Groups.Io <chris1011@...> wrote:

That's really nice. Sharp and great color.

A question: do you think that 1600mm is a sweet spot for all kinds of deep sky imaging, especially for high resolution work? Especially since the newer Cmos cameras have such small pixels and would be able to take advantage of a high resolution optic for small faint galaxies.

Rolando

-----Original Message-----
From: Robert Chozick via Groups.Io <rchozick@...>
To: main <main@ap-gto.groups.io>
Sent: Fri, Feb 14, 2020 12:06 am
Subject: [ap-gto] Close up of M81 without CCDT67

I got another shot of M 81 on the same trip as the M81-82 image, this time at f/8 1620mm.

https://pbase.com/image/170419535

Robert Chozick

rchozick@...

Robert Chozick

rchozick@...

Robert Chozick

rchozick@...